A conventional communications system such as a 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) communications system includes some communications controllers such as a base station and an evolved NodeB (eNodeB), and communications devices such as user equipment (UE) and a mobile station. In the LTE system, a link on which sending is performed from the eNodeB to the UE is referred to as a downlink, and a link on which sending is performed from the UE to the eNodeB is referred to as an uplink. Data sent by the eNodeB to the UE is carried at a physical layer by using a physical downlink shared channel (PDSCH); data sent by the UE to the eNodeB is carried at a physical layer by using a physical uplink shared channel (PUSCH). The eNodeB indicates, to the UE by using a physical downlink control channel (PDCCH), a frequency domain resource and a transmission manner used by the PDSCH and/or PUSCH; the UE indicates a hybrid automatic repeat request-acknowledgement (HARQ-ACK) and a channel quality indicator (CQI) to the eNodeB by using a physical uplink control channel (PUCCH).
In a conventional Long Term Evolution-Advanced (LTE-A) communications system, a carrier aggregation (CA) technology can be supported, that is, two or more than two component carriers (CC) can be aggregated together and used for data transmission to support larger bandwidth, where bandwidth of each CC can reach 20 MHz. For example, in uplink CA, UE supports data transmission on two uplink CCs, and therefore, an eNodeB can perform scheduling on the UE to perform PUSCH transmission on the two uplink CCs, where the two uplink CCs include a primary component carrier (PCC) and a secondary component carrier (SCC), and correspondingly, cells respectively corresponding to two carriers are referred to as a primary cell (Pcell) and a secondary cell (Scell).
FIG. 1 is a schematic diagram of a conventional CA technology. As shown in FIG. 1, uplink CA is used as an example, and it is assumed that two cells under control of an eNodeB respectively use a CC1 (which may be correspondingly referred to as a PCC) and a CC2 (which may be correspondingly referred to as an SCC), where the cell using the CC1 is a Pcell, and the cell using the CC2 is an Scell. Further, the Pcell may schedule, by using a scheduling grant 1, UE to send PUSCH1 on an uplink of the Pcell and the Scell may schedule, by using a scheduling grant 2, the UE to send PUSCH2 on an uplink of the Scell.
CA defined in a conventional 3GPP LTE R11 standard is established on the assumption of ideal backhaul, that is, backhaul between different network devices of CCs or between different units of a same network device of CCs is controlled to have a quite low time delay, and information exchange can be rapidly performed, and therefore, scheduling of the CCs on UE can be dynamically coordinated. For example, for CA in a same eNodeB shown in FIG. 1, that is, multiple cells under control of an eNodeB use different CCs; when the cells may jointly serve a user by means of carrier aggregation, backhaul between the cells is ideal and information exchange can be rapidly performed because these multiple cells belong to the same eNodeB.
In a conventional communications system, when user equipment (UE) has a multi-carrier transmission capability, multiple carriers may be configured for the UE to serve the UE, that is, carrier aggregation (CA). In a CA technology, UE may configure maximum transmit power for each carrier, and may report a power headroom (PH) of a cell corresponding to each carrier to an eNodeB, so that the eNodeB can obtain information about residual power of the UE according to the PH, thereby determining radio resource power scheduled for the UE. However, a value of total transmit power of the UE on multiple carriers still needs to satisfy maximum transmit power determined by requirements in an aspect of human health, network configurations, and the like.
The conventional CA technology is based on the assumption of ideal backhaul, that is, information exchange between different cells has a quite low time delay and a quite large capacity. A cell can acquire dynamic information of another cell in time, and therefore, a radio resource is scheduled for UE according to the dynamic information. The cell may be controlled by a same eNodeB or different eNodeBs.
However, in actual application, due to factors such as an environment and costs of deploying a communications device such as an eNodeB, implementation of ideal backhaul is quite difficult. In non-ideal backhaul, a time delay of information exchange between eNodeBs or between different units of an eNodeB is relatively large. For example, a cell controlled by different eNodeBs can only acquire a PH, reported by UE, of another cell; therefore, a case in which total transmit power needed by the UE on carriers exceeds allowed maximum transmit power. As a result, the UE performs power compression, a transmission error probability increases, and a loss of an uplink throughput of the UE occurs; in addition, a case of resource waste may occur because transmit power of the UE on each carrier is quite small.